Semiconductor Device

ABSTRACT

Diffusion layers  2 - 5  are formed on a silicon substrate  1,  and gate dielectric films  6, 7  and gate electrodes  8, 9  are formed on these diffusion layers  2 - 5  so as to be MOS transistors. Zirconium oxide or hafnium oxide is used as a major component of gate dielectric films  6, 7.  Gate dielectric films  6, 7  are formed, for example, by CVD. As substrate  1,  there is used one of which the surface is (111) crystal face so as to prevent diffusion of oxygen into silicon substrate  1  or gate electrodes  8, 9.  In case of using a substrate of which the surface is (111) crystal face, diffusion coefficient of oxygen is less than 1/100 of the case in which a silicon substrate of which the surface is (001) crystal face is used, and oxygen diffusion is controlled. Thus, oxygen diffusion is controlled, generation of leakage current is prevented and properties are improved. There is realized a semiconductor device having high reliability and capable of preventing deterioration of characteristics concomitant to miniaturization.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device using a highdielectric constant material.

With miniaturization of semiconductor devices in recent years, it isrequired that the gate length in transistors be reduced to 0.15 μm andthe gate dielectric film thickness to not more than 2 nm when SiO₂ isused for such an insulating film. Slimming of the insulating film to athickness of not more than 2 nm enlarges tunnel current to anunignorable degree.

As a solution to this problem, it has been proposed to use an insulatingmaterial with a higher dielectric constant than SiO₂ so as to increasethe physical film thickness while maintaining the desirable dielectricproperties. Among the candidates for the high dielectric constantmaterials having potentialities to satisfy the above requirements arezirconium oxide and hafnium oxide as described in the February, 2000,issue of NIKKEI MICRODEVICES (pages 93-106).

SUMMARY OF THE INVENTION

Zirconium oxide and hafnium oxide, however, form a reaction compoundwith a film thickness of about 1.5 to 2.5 nm at the interface with asilicon substrate as described in, for instance, papers presented in1999 IEEE (The Institute of Electrical and Electronics Engineers)International Electron Devices Meeting (Presentation No. 6.1 on pages133-136, and Presentation No. 6.4 on pages 145-148).

This reaction compound is formed as oxygen gets away from zirconiumoxide or hafnium oxide and is diffused into the silicon substrate, soformation of such a reaction compound indicates the occurrence of oxygendeficiency in zirconium oxide or hafnium oxide. This oxygen deficiencyis causative of the detrimental phenomena for the properties ofsemiconductor devices, such as increase of leakage current.

Also, oxygen may be diffused from the gate dielectric films mostlycomposed of zirconium oxide or hafnium oxide to the gate electrodes toinduce oxygen deficiency. This, too, is causative of propertydeterioration of semiconductor devices.

The above-mentioned problems relating to the reaction compound fromzirconium oxide or hafnium oxide and silicon substrate also exist insemiconductor devices having a thin film transistor (TFT) structure.

Thus, the reaction compound from polycrystalline silicon film andzirconium oxide or hafnium oxide is that formed as oxygen is liberatedfrom zirconium oxide or hafnium oxide and diffused to polycrystallinesilicon film, and this means that oxygen deficiency occurs in zirconiumoxide or hafnium oxide.

The first object of the present invention is to realize a semiconductordevice with high reliability, which is proof against deterioration ofdielectric properties concomitant to structural miniaturization.

The second object of the present invention is to realize a miniaturizedsemiconductor device, which can be produced in high yield.

The third object of the present invention is to realize a semiconductordevice having a gate structure resistant to diffusion of oxygen throughthe interface between silicon substrate and gate dielectric films.

The fourth object of the present invention is to realize a semiconductordevice having a thin film transistor structure, which obstructsdiffusion of oxygen through the interface between silicon film and gatedielectric films.

As a result of the studies for finding means for reducing diffusion ofoxygen from the insulating films mostly composed of zirconium oxide orhafnium oxide, the present inventors have found that it is of avail forthe above purpose to use a silicon substrate of which the surface is(111) crystal face instead of such a silicon substrate of which thesurface is (001) crystal face as used in the conventional semiconductordevices.

They have also found that incorporation of hafnium or titanium inzirconium oxide, or incorporation of titanium in hafnium oxide, of theinsulating film is effective for further suppressing diffusion ofoxygen.

They have further found that the electrode materials which resistdiffusion of oxygen through the interface with insulating films mostlycomposed of zirconium oxide or hafnium oxide are cobalt silicide andsilicon. In this connection, (100) crystal face and (010) crystal faceare equivalent to (001) crystal face.

They have further found that use of polycrystalline silicon film having(111) orientation is effective for semiconductor devices having TFTstructure.

In order to attain the above objects, the present invention is embodiedas described below. In the present specification and claims, anabbreviation “at. %” is used to represent “atomic %”.

-   (1) A semiconductor device comprising a silicon substrate, gate    dielectric films mostly composed of zirconium oxide and formed on a    major surface of said silicon substrate, and gate electrode films    formed in contact with said gate dielectric films, said major    surface of said silicon substrate being parallel to Si (111) crystal    face.-   (2) Preferably, a semiconductor device described in (1) above,    wherein the main constituent of said gate electrode films is cobalt    silicide or silicon.-   (3) Also preferably, a semiconductor device of (2) above, wherein    said gate dielectric films contain hafnium in a concentration of    from 0.01 at. % inclusive to 15 at. % inclusive.-   (4) Also preferably, a semiconductor device of (2) above, wherein    said gate dielectric films contain hafnium in a concentration of    from 0.04 at. % inclusive to 12 at. % inclusive.-   (5) Also preferably, a semiconductor device of (2) above, wherein    said gate dielectric films contain titanium in a concentration of    from 0.005 at. % inclusive to 15 at. % inclusive.-   (6) Also preferably, a semiconductor device of (2) above, wherein    said gate dielectric films contain titanium in a concentration of    from 0.02 at. % inclusive to 8 at. % inclusive.-   (7) A semiconductor device comprising a silicon substrate, gate    dielectric films mostly composed of hafnium oxide and formed on a    major surface of said silicon substrate, and gate electrode films    formed in contact with said gate dielectric films, said major    surface of silicon substrate being parallel to Si (111) crystal    face.-   (8) Preferably, a semiconductor device of (7) above, wherein said    gate electrode films are mostly composed of cobalt silicide or    silicon.-   (9) Also preferably, a semiconductor device of (8) above, wherein    said gate dielectric films contain titanium in a concentration of    from 0.01 at. % inclusive to 15 at. % inclusive.-   (10) Also preferably, a semiconductor device of (8) above, wherein    said gate dielectric films contain titanium in a concentration of    from 0.03 at. % inclusive to 10 at. % inclusive.-   (11) A semiconductor device comprising a substrate, silicon films    formed on a major surface of said substrate, gate dielectric films    formed in contact with said silicon films, and gate electrode films    formed in contact with said gate dielectric films, said silicon    films having (111) orientation, and said gate dielectric films being    mostly composed of zirconium oxide.-   (12) A semiconductor device comprising a substrate, silicon films    formed on a major surface of said substrate, gate dielectric films    formed in contact with said silicon films, and gate electrode films    formed in contact with said gate dielectric films, said silicon    films having (111) orientation, and said gate dielectric films being    mostly composed of hafnium oxide.-   (13) A semiconductor device comprising a substrate, insulating films    formed on a major surface of said substrate, silicon films formed in    contact with said insulating films, gate dielectric films formed in    contact with said silicon films, and gate electrode films formed in    contact with said gate dielectric films, said silicon films    having (111) orientation, said insulating films being mostly    composed of hafnium oxide or zirconium oxide, and said gate    dielectric films being mostly composed of hafnium oxide or zirconium    oxide.

With progress of integration and miniaturization of semiconductordevices in recent years, reduction of contact resistance of the sectionwhere silicon substrate is connected to metal wiring for high speedoperation is required. As prior art for reducing contact resistance, ithas been proposed to form a cobalt silicide film on a diffusion layer(source/drain) or polycrystalline silicon electrode on a siliconsubstrate as described in JP-A-08-78357.

However, as a result of miniaturization of semiconductor devices, thediffusion layer has become shallow, and slimming of the cobalt silicidefilms becomes necessary. Slimming of the cobalt silicide films has givenrise to the problem that due to high-temperature heat treatment in theproduction steps, for example memory capacitor forming step, cobaltatoms in the cobalt silicide films are diffused into the siliconsubstrate, reducing the thickness of cobalt silicide film excessively inparts to cause local elevation of resistance. This problem becomes moreserious in case of using a high dielectric constant material such astantalum oxide for the capacitor insulating film for higher integrationof memory capacitor.

This is for the reason that in case a high dielectric constant materialsuch as tantalum oxide is used, a heat treatment at elevatedtemperatures of about 700° C. or above is required for the stabilizationof dielectric properties, and such a treatment promotes diffusion ofcobalt atoms into silicon substrate. The similar problem occurs in thecase of nickel silicide film. That is, when nickel silicide film isslimmed, nickel atoms in this nickel silicide film are diffused intosilicon substrate by heat treatment and the thickness of nickel silicidefilm is reduced excessievely in parts to cause rise of resistance.

In quest for a solution to this and above-mentioned problems, thepresent inventors have pursued extensive studies for finding means forpreventing diffusion of cobalt atoms to silicon substrate andconsequently found that it is effective for the above purpose to use asilicon substrate of which the surface is (111) crystal face instead ofa silicon substrate of which the surface is (001) crystal face, whichhas been used in the conventional semiconductor devices. Further, as aresult of studies for obtaining means for preventing diffusion of cobaltatoms from conductive film mostly composed of nickel silicide intosilicon substrate, the present inventors have found that it is alsoeffective to use a silicon substrate of which the surface is (111)crystal face instead of using a silicon substrate of which the surfaceis (001) crystal face. Still further, as a result of researches foracquiring means for preventing diffusion of oxygen from insulating filmsmostly composed of zirconium oxide or hafnium oxide, the presentinventors have found that it is effective to use a silicon substrate ofwhich the surface is (111) crystal face instead of a silicon substrateof which the surface is (001) crystal face, which is used in theconventional semiconductor devices. They have further found that inorder to prevent diffusion of oxygen, it is effective to incorporatehafnium or titanium in zirconium oxide or incorporate titanium inhafnium oxide. Moreover, they have found that the electrode materialsthat prevent diffusion of oxygen through the interface with insulatingfilms mostly composed of zirconium oxide or hafnium oxide are cobaltsilicide and silicon. In this connection, (100) crystal face and (010)crystal face are equivalent to (001) crystal face. Preferred use of(001) crystal face instead of (111) crystal face in the past isattributable to the difficulties involved in forming high-qualitysilicon oxide film on (111) crystal face. This problem, however, can beeliminated by forming an insulating film mostly composed of zirconiumoxide or hafnium oxide instead of silicon oxide film, because this filmcan be easily formed on (111) crystal face.

The above objects of the present invention can be achieved, for example,by providing the semiconductor devices having the structures describedbelow.

-   (14) A semiconductor device comprising a silicon substrate, gate    dielectric films formed on a major surface of said silicon    substrate, gate electrode films formed on said gate dielectric    films, and wiring films mostly composed of cobalt silicide or nickel    silicide, said major surface being formed so as to be (111) crystal    face of the substrate.

The expression “said major surface is formed so as to be (111) crystalface of the substrate” used here includes the case where said majorsurface is parallel to Si (111) crystal face.

A semiconductor device described above, wherein said gate dielectricfilms are mostly composed of zirconium oxide.

A semiconductor device described above, wherein said gate electrodefilms are mostly composed of cobalt silicide or silicon.

A semiconductor device described above, wherein said gate dielectricfilms contain hafnium in a concentration of from 0.01 at. % inclusive to15 at. % inclusive.

A semiconductor device described above, wherein said gate dielectricfilms contain titanium in a concentration of from 0.005 at. % inclusiveto 15 at. % inclusive.

-   (15) A semiconductor device comprising a silicon substrate, gate    dielectric films formed on a major surface of said silicon    substrate, gate electrode films formed on said gate dielectric    films, and wiring films mostly composed of cobalt silicide or nickel    silicide, said gate dielectric films being mostly composed of    hafnium oxide, and said major surface being formed so as to be    Si (111) crystal face.

A semiconductor device described above, wherein said gate electrodefilms are mostly composed of cobalt silicide or silicon.

A semiconductor device described above, wherein said gate dielectricfilms contain titanium in a concentration of from 0.02 at. % inclusiveto 8 at. % inclusive.

-   (16) A semiconductor device comprising a silicon substrate, gate    dielectric films formed on a major surface of said silicon    substrate, gate electrode films formed on said gate dielectric    films, wiring films mostly composed of cobalt silicide or nickel    silicide, and a memory capacitor having a high dielectric constant    material as capacitor insulating film, said gate dielectric films    being mostly composed of zirconium oxide, and said major surface of    the substrate being parallel to Si (111) crystal face.-   (17) A semiconductor device comprising a silicon substrate, gate    dielectric films formed on a major surface of said silicon    substrate, gate electrode films formed on said gate dielectric    films, wiring films mostly composed of cobalt silicide or nickel    silicide, and a memory capacitor having a high dielectric constant    material as capacitor insulating film, said gate dielectric films    being mostly composed of hafnium oxide, and said major surface being    parallel to Si (111) crystal face.-   (18) A semiconductor device comprising a silicon substrate, gate    dielectric films formed on a major surface of said silicon    substrate, gate electrode films formed on said gate dielectric    films, wiring layers formed at a higher position than the gate    electrodes, diffusion layers containing an additional element and    formed on said silicon substrate in correspondence to said gate    electrodes, and contact holes formed between said diffusion layers    and said wiring layers, each of said contact holes having a wiring    film mostly composed of cobalt silicide or nickel silicide and    formed on said diffusion layer as well as a conductive film formed    on said wiring film, said gate dielectric films being mostly    composed of zirconium oxide or hafnium oxide, and said major surface    being formed so as to be (111) crystal face of the substrate.

A semiconductor device comprising a semiconductor substrate, gatedielectric films formed on a major surface of said semiconductorsubstrate, gate electrode films formed on said gate dielectric films,diffusion layers containing an additional element, wiring layers formedabove said gate electrode films, and contact holes formed between saiddiffusion layers and said wiring layers, each of said contact holeshaving a wiring film mostly composed of cobalt silicide or nickelsilicide and formed on said diffusion layer as well as a conductive filmformed on said wiring film, said major surface being formed so as to be(111) crystal face of the substrate.

A semiconductor device comprising a semiconductor substrate, gatedielectric films formed on a major surface of said semiconductorsubstrate, gate electrode films formed on said gate dielectric films,contact holes, and wiring layers formed above the gate electrodes and onsaid contact holes, each of said contact holes having a wiring filmmostly composed of cobalt silicide or nickel silicide and a conductivefilm formed on said wiring film, and said major surface being parallelto Si (111) crystal face.

The semiconductor device according to the invention can comprise, inaddition to the above-mentioned structural elements, gate dielectricfilms having a first layer mostly composed of silicon oxide, zirconiumsilicate or hafnium silicate, and a second layer mostly composed ofzirconium oxide or hafnium oxide formed on said first layer.

It also can comprise, in addition to the above-mentioned structuralelements, a first layer mostly composed of cobalt silicide or silicon,and a second layer mostly composed of tungsten or molybdenum formed onsaid first layer, said major surface being parallel to Si (111) crystalface. It also can have a third layer mostly composed of titanium nitrideor tungsten nitride formed between said first and second layers.

The other objects, features and advantages of the present invention willbecome apparent from the following description of the embodiments of thepresent invention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the principal part of the semiconductordevice in the first embodiment of the present invention.

FIG. 2 is a diagram that compares the diffusion coefficient of cobaltwhen cobalt in a 3 nm thick cobalt silicide film was diffused into asilicon substrate of which the surface is (001) crystal face with thediffusion coefficient of cobalt when cobalt in a 3 nm thick cobaltsilicide film was diffused into a silicon substrate of which the surfaceis (111) crystal face according to the present invention.

FIG. 3 is a diagram that compares the diffusion coefficient of nickelwhen nickel in a 3 nm thick nickel silicide film was diffused into asilicon substrate of which the surface is (001) crystal face and thediffusion coefficient of nickel when nickel in a 3 nm thick nickelsilicide film was diffused into a silicon substrate of which the surfaceis (111) crystal face according to the the present invention.

FIG. 4 is a diagram that compares the diffusion coefficient of oxygen at300° C. when oxygen in a 3 nm thick zirconium oxide film was diffusedinto a silicon substrate of which the surface is (001) crystal face andthe diffusion coefficient of oxygen at 300° C. when oxygen in a 3 nmthick zirconium oxide film was diffused into a silicon substrate ofwhich the surface is (111) crystal face according to the presentinvention.

FIG. 5 is a diagram that compares the diffusion coefficient of oxygen at300° C. when oxygen in a 3 nm thick hafnium oxide film was diffused intoa silicon substrate of which the surface is (001) crystal face and thediffusion coefficient of oxygen at 300° C. when oxygen in a 3 nm thickhafnium oxide film was diffused into a silicon substrate of which thesurface is (111) crystal face according to the present invention.

FIG. 6 is a graph showing diffusion coefficient of oxygen at 300° C.when oxygen in a 3 nm thick zirconium oxide film was diffused into asilicon substrate according to the present invention in low additionalelement concentration region.

FIG. 7 is a graph showing diffusion coefficient of oxygen at 300° C.when oxygen in a 3 nm thick zirconium oxide film was diffused into asilicon substrate according to the present invention in high additionalelement concentration region.

FIG. 8 is a graph showing diffusion coefficient of oxygen at 300° C.when oxygen in a 3 nm thick hafnium oxide film was diffused into asilicon substrate according to the present invention in low additionalelement concentration region.

FIG. 9 is a graph showing diffusion coefficient of oxygen at 300° C.when oxygen in a 3 nm thick hafnium oxide film was diffused into asilicon substrate according to the present invention in high additionalelement concentration region.

FIG. 10 is a graph showing diffusion coefficient of oxygen at 300° C.when using an analytical model of a structure having a 3 nm thickelectrode film formed on a 3 nm thick zirconium oxide film according tothe present invention in low additional element concentration region.

FIG. 11 is a graph showing diffusion coefficient of oxygen at 300° C.when using an analytical model of a structure having a 3 nm thickelectrode film formed on a 3 nm thick zirconium oxide according to thepresent invention in high additional element concentration region.

FIG. 12 is a graph showing diffusion coefficient of oxygen at 300° C.when using an analytical model of a structure having a 3 nm thickelectrode film formed on a 3 nm thick hafnium oxide film according tothe present invention in low additional element concentration region.

FIG. 13 is a graph showing diffusion coefficient of oxygen at 300° C.when using an analytical model of a structure having a 3 nm thickelectrode film formed on a 3 nm thick hafnium oxide film according tothe present invention in high additional element concentration region.

FIG. 14 is a diagram showing diffusion coefficients of oxygen forvarious types of electrode material by using an analytical model of astructure having a 3 nm thick electrode film formed on a 3 nm thickzirconium oxide.

FIG. 15 is a diagram showing diffusion coefficients of oxygen forvarious types of electrode material by using an analytical model of astructure having a 3 nm thick electrode film formed on a 3 nm thickhafnium oxide.

FIG. 16 is a sectional view of the principal part of the semiconductordevice in the second embodiment of the present invention.

FIG. 17 is a sectional view of the principal part of the semiconductordevice in the third embodiment of the present invention.

FIG. 18 is a sectional view of the principal part of the semiconductordevice in the fourth embodiment of the present invention.

FIG. 19 is a sectional view of the TFT structure of the semiconductordevice in the fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The mode of practice of the present invention is explained in moredetail with reference to the embodiments thereof shown in the drawings.

A sectional structure of the principal part of the semiconductor devicein the first embodiment of the present invention is shown in FIG. 1.

In the semiconductor device according to the first embodiment of thepresent invention, as illustrated in FIG. 1, diffusion layers 2, 3, 4, 5are formed on a silicon substrate 1, and gate dielectric films 6, 7 andgate electrodes 8, 9 are formed on these diffusion layers 2, 3, 4, 5 toconstitute MOS transistors.

Zirconium oxide or hafnium oxide is used as the main constituent of saidgate dielectric films 6, 7 for meeting the requirements forminiaturization and high functionality.

These gate dielectric films 6, 7 can be formed, for example, by chemicalvapor deposition (CVD) or sputtering.

A substrate of which the surface is (111) crystal face is used assilicon substrate 1 so that oxygen will not be allowed to diffuse easilyinto silicon substrate 1 or gate electrodes 8, 9 during heat treatment.In the semiconductor device of the instant embodiment, as shown in FIG.1, diffusion layers 2, 3, 4, 5 having an additional element such asarsenic, phosphorus, boron or antimony diffused therein are formed onsilicon substrate 1, and gate dielectric films 6, 7 and gate electrodes8, 9 are formed thereon to constitute MOS transistors. Zirconium oxideor hafnium oxide is used as the main constituent of said gate dielectricfilms 6, 7 for meeting the requirements for miniaturization and highfunctionality of the device. For the insulating films comprising a highdielectric constant material such as mentioned above, there is used, forexample, a material having a dielectric constant of 10 or greater.

These gate dielectric films 6, 7 can be formed by, for example, CVD orsputtering. A substrate of which the surface is (111) crystal face isused as silicon substrate 1 so as to prevent diffusion of oxygen intosilicon substrate 1 or gate electrodes 8, 9 during heat treatment. Incase of using zirconium oxide as the main constituent of gate dielectricfilms 6, 7, it is more preferable to contain hafnium or titanium asadditional element in said dielectric films 6, 7. In case of usinghafnium oxide as the main constituent of gate dielectric films 6, 7, itis more preferable to contain titanium as additional element in saidgate dielectric films 6, 7. It is more preferable to use cobalt silicideor silicon as the main constituent of gate electrodes 8, 9 forpreventing diffusion of oxygen from gate dielectric films 6, 7 duringheat treatment. These gate electrodes 8, 9 can be formed, for example,by CVD or sputtering. MOS transistors are separated, for instance, by anelement separating film 10 comprising a silicon oxide film. Insulatingfilms 11, 12 comprising, for example, a silicon oxide film are formedover the top and side walls of said gate electrodes 8, 9.

The top of each MOS transistor is entirely covered with an insulatingfilm 13 comprising, for example, a boron-doped phospho silicate glass(BPSG) film or spin-on-glass (SOG) film, or a silicon oxide or nitridefilm formed by CVD or sputtering. Contact holes are formed in saidinsulating film 13, and in each of said contact holes are formed awiring film 14 for contact, mostly composed of cobalt silicide or nickelsilicide, and a plug 15, which are connected to diffusion layers 2, 3,4, 5. Since a substrate of which the surface is (111) crystal face isused as silicon substrate 1, diffusion of cobalt atoms or nickel atomsfrom said wiring film 14 into silicon substrate 1 is discouraged. Firstlaminate wiring comprising main conductive film 17 covered by adjoiningconductor films 16 a, 16 b for preventing diffusion is connected throughplug 15. Plug 15 on wiring film 14 can be a deposition of conductivefilm, which can be a film mostly composed of tungsten. It is alsopossible to form a film, for example, a film of titanium nitride, on theoutside of said conductive film. This laminate wiring can be obtained,for example, by forming adjacent conductor film 16 a by sputtering orother means, then forming main conductor film 17 by sputtering or othermeans, further forming thereon another adjacent conductor film 16 b bysputtering or other means, and then forming a wiring pattern by etching.

On said first laminate wiring, a plug comprising main conductor film 20covered by adjacent conductor film 19 is formed in a contact hole formedin insulating film 21, which plug is connected to said first laminatewiring. Through this plug is connected second laminate wiring comprisingmain conductor film 23 covered by adjacent conductor films 22 a, 22 b.This second laminate wiring can be obtained, for example, by formingadjacent conductor film 22 a by sputtering or other means, then formingmain conductor film 23 by sputtering or other means, further formingthereon another adjacent conductor film 22 b by sputtering or othermeans, and then forming a wiring pattern by etching.

The diffusion preventing effect in the instant embodiment of theinvention is explained below. To explain the advantage of thisembodiment in detail, there is shown here an analytical example usingmolecular dynamic simulation. Molecular dynamic simulation is a systemin which, as described for instance in Journal of Applied Physics, Vol.54, 1983, pp. 4,864-4,878, the forces working to each atom throughinteratomic potential are calculated, and based on the calculatedforces, Newton's equations of motion are solved to determine theposition of each atom at each time point.

In the instant embodiment, the following relationships were determinedby calculating the interactions between different elements byintroducing charge transfer into said molecular dynamic system.

A salient advantage of the instant embodiment is that diffusion ofcobalt atoms or nickel atoms from wiring film 14 into silicon substrate1 is prevented by use of a silicon substrate of which the surface is(111) crystal face instead of a silicon substrate of which the surfaceis (001) crystal face employed in the conventional semiconductordevices. This controls generation of leakage current and other troublesto realize a semiconductor device with improved performance. It is alsoa salient advantage of the present embodiment that diffusion of oxygenfrom gate dielectric films 6, 7 into silicon substrate is prevented. Asalient advantage of the instant embodiment is that diffusion of oxygenfrom gate dielectric films into silicon substrate is prevented byincorporating an additional element in gate dielectric films 6, 7.Another advantage of the instant embodiment is that diffusion of oxygenfrom gate dielectric films 6, 7 into gate electrodes is controlled byincorporating an additional element in said gate dielectric films. So,the effects of the instant embodiment of the present invention can beanalyzed by calculating the diffusion coefficients of cobalt, nickel andoxygen. The method of calculating the diffusion coefficients bymolecular dynamic simulation is described in, for instance, PhysicalReview B, Vol. 29 (1984), pp. 5,363-5,371.

First, an advantage of the instant embodiment of the present inventionis demonstrated by showing a calculation example using as analyticalmodel a structure in which a 3 nm thick cobalt silicide film is formedon a 10 nm silicon substrate of which the surface is (001) crystal faceand a structure in which a 3 nm thick cobalt silicide film is formed ona 10 nm thick silicon substrate of which the surface is (111) crystalface. FIG. 2 shows the result of calculation of the ratio of cobaltdiffusion coefficient D in the case where cobalt in the cobalt silicidefilm is diffused into silicon substrate. In FIG. 2, the diffusioncoefficient in the case where a silicon substrate of which the surfaceis (001) crystal face is used is represented by D_(R), and the ratio ofD to D_(R) is shown. As is seen from this diagram, the diffusioncoefficient in the case where a silicon substrate of which the surfaceis (111) crystal face is used is less than 1/100 that of the case wherea silicon substrate of which the surface is (001) crystal face is used,which verifies the advantage of suppressing diffusion of cobalt by useof a silicon substrate of which the surface is (111) crystal face. Thus,in this case, diffusion of cobalt from cobalt silicide film into siliconsubstrate is controlled, preventing rise of resistance.

Next, an advantage of the instant embodiment using a silicon substrateof which the surface is (111) crystal face is demonstrated by showing acalculation example using as analytical model a structure in which a 3nm thick nickel silicide film is formed on a 10 nm thick siliconsubstrate of which the surface is (001) crystal face and a structure inwhich a 3 nm thick nickel silicide film is formed on a 10 nm siliconsubstrate of which the surface is (111) crystal face. FIG. 3 shows theresult of calculation of the ratio of nickel diffusion coefficient D inthe case where nickel in the nickel silicide film is diffused intosilicon substrate. In FIG. 3, the diffusion coefficient in the casewhere a silicon substrate of which the surface is (001) crystal face isused is represented by D_(R), and the ratio of D to D_(R) is shown. Asis seen from this diagram, the diffusion coefficient in the case where asilicon substrate of which the surface is (111) crystal face is used isless than 1/100 that of the case where a silicon substrate of which thesurface is (001) crystal face is used, which demonstrates the advantageof controlling diffusion of nickel by use of a silicon substrate ofwhich the surface is (111) crystal face. Thus, in this case, diffusionof nickel from nickel silicide film into silicon substrate iscontrolled, preventing rise of resistance.

Next, an advantage of the instant embodiment using a silicon substrateof which the surface is (111) crystal face is demonstrated by showing acalculation example using as analytical model a structure in which a 3nm thick gate dielectric film is formed on a 10 nm thick siliconsubstrate of which the surface is (001) crystal face and a structure inwhich a 3 nm thick gate dielectric film is formed on a 10 nm thicksilicon substrate of which the surface is (111) crystal face. FIG. 4shows the result of calculation of the ratio of diffusion coefficient Dof oxygen in the case where oxygen in zirconium oxide film (gatedielectric film) is diffused into silicon substrate at 300° C. In FIG.4, diffusion coefficient in the case where a silicon substrate of whichthe surface is (001) crystal face is used is represented by D_(R), andthe ratio of D to D_(R) is shown. As is seen from the diagram, thediffusion coefficient in the case where a silicon substrate of which thesurface is (111) crystal face is used is less than 1/100 that of thecase where a silicon substrate of which the surface is (001) crystalface is used, indicating the advantage of suppressing diffusion ofoxygen in the former case. Thus, in this case, diffusion of oxygen fromgate dielectric film into silicon substrate is prevented, making it lessliable for zirconium oxide to suffer oxygen deficiency. The result ofsimilar calculation in case of using hafnium oxide instead of zirconiumoxide as gate dielectric film is shown in FIG. 5. In this diagram, likein the case of FIG. 4, diffusion coefficient in the case where a siliconsubstrate of which the surface is (001) crystal face is used isrepresented by D_(R), and the ratio of D to D_(R) is shown. As is seenfrom this diagram, the diffusion coefficient in the case where a siliconsubstrate of which the surface is (111) crystal face is used is lessthan 1/100 that of the case where a silicon substrate of which thesurface is (001) crystal face is used, demonstrating the advantage ofsuppressing diffusion of oxygen in the former case. Thus, in this case,diffusion of oxygen from gate dielectric film into silicon substrate isprevented, making it less liable for hafnium oxide to suffer oxygendeficiency.

Next, the effect of additional elements in the instant embodiment isdemonstrated by showing a calculation example using as analytical modela structure in which a 3 nm thick gate dielectric film is formed on a 10nm thick silicon substrate of which the surface is (111) crystal face.FIGS. 6 and 7 show the results of calculation of the ratio of diffusioncoefficient D of oxygen in the case where oxygen in zirconium oxide film(gate dielectric film) was diffused into silicon substrate at 300° C. D₀indicates diffusion coefficient of oxygen when no additional element iscontained. FIG. 6 shows additional element concentration dependency ofD/D₀ in the low concentration region, and FIG. 7 shows additionalelement concentration dependency of D/D₀ in the high concentrationregion. It can be seen from FIG. 6 that when hafnium is added in aconcentration of 0.01 at. % or more in zirconium oxide film, diffusioncoefficient is reduced as compared with the case of no addition ofhafnium, and when hafnium is added in a concentration of 0.04 at. % ormore, diffusion coefficient is unexpectedly reduced to about 1/13 thatof the case of no addition.

It is also seen that when titanium is added in a concentration of 0.005at. % or more into zirconium oxide film, diffusion coefficient isreduced as compared with the case of no addition, and when titanium isadded in a concentration of 0.02 at. % or more, diffusion coefficient isunexpectedly reduced to about 1/11 that of the case of no addition.

Referring to FIG. 7, it is noted that a diffusion coefficient reducingeffect can be obtained until the hafnium concentration reaches 15 at. %,but this effect is weakened when the hafnium concentration becomes 12at. % or higher. It can be also learned that a diffusion coefficientreducing effect can be obtained until the titanium concentration reaches15 at. %, but the effect weakened when the titanium concentrationbecomes 8 at. % or higher.

Thus, it is possible to reduce diffusion of oxygen by adding hafnium ina concentration of from 0.01 at. % inclusive to 15 at. % inclusive ortitanium in a concentration of from 0.005 at. % inclusive to 15 at. %inclusive into a film mostly composed of zirconium oxide.

Further, diffusion of oxygen can be reduced steadily and more intenselyby adding hafnium in a concentration of from 0.04 at. % inclusive to 12at. % inclusive or titanium in a concentration of from 0.02 at. %inclusive to 8 at. % inclusive into a film mostly composed of zirconiumoxide.

The above-described advantages of the first embodiment of the presentinvention can be obtained with little variation even if the calculationconditions such as film thickness and temperature are changed.

FIGS. 8 and 9 show the results of calculation of the ratio of diffusioncoefficient D of oxygen in the case where oxygen in hafnium oxide film(gate dielectric film) is diffused into silicon substrate in ananalytical model similar to those of FIGS. 6 and 7. D₀ indicatesdiffusion coefficient of oxygen when no additional element is contained.FIG. 8 shows additional element concentration dependency of D/D₀ in thelow concentration region.

It is seen from FIG. 8 that when titanium is added in a concentration of0.01 at. % or more in hafnium oxide film, diffusion coefficient isreduced as compared with the case of no addition of titanium, and whentitanium is added in a concentration of 0.03 at. % or more, diffusioncoefficient is unexpectedly reduced to about 1/13 that of the case of noaddition.

It can be also learned from FIG. 9 that there can be obtained asignificant diffusion coefficient reducing effect until titaniumconcentration goes up to 15 at. %, but the effect is weakened whentitanium concentration becomes 10 at. % or higher.

It is thus possible to reduce diffusion of oxygen by adding titanium ina concentration of from 0.01 at. % inclusive to 15 at. % inclusive in afilm mostly composed of hafnium oxide.

Oxygen diffusion can be further prevented more intensely and steadily byadding titanium in a concentration of from 0.03 at. % inclusive to 10at. % inclusive into a film mostly composed of hafnium oxide.

The advantages of the present invention described above can be obtainedwith little variation even if the calculation conditions such as filmthickness and temperature are changed.

Next, as another advantage of the instant embodiment, it is demonstratedby molecular dynamic analytical examples that diffusion of oxygen fromgate dielectric film into gate electrodes can be controlled byincorporating an additional element into the film. Here, there is showna case where diffusion coefficient of oxygen at 300° C. is calculated byusing as analytical model a structure in which a 3 nm thick electrodefilm is formed on a 3 nm thick gate dielectric film. FIGS. 10 and 11show the results obtained from the case where zirconium oxide is used asgate dielectric film and cobalt silicide film and silicon film are usedas electrodes. D₀ indicates diffusion coefficient of oxygen when noadditional element is incorporated. FIG. 10 shows additional elementconcentration dependency of D/D₀ in the low concentration region, andFIG. 11 shows additional element concentration dependency of D/D₀ in thehigh concentration region.

From FIG. 10, it is noted that, as in the case of FIG. 6, when hafniumis added in a concentration of 0.01 at. % or more into zirconium oxidefilm, diffusion coefficient is reduced as compared with the case of noaddition of hafnium, and when it is added in a concentration of 0.04 at.% or more, diffusion coefficient is unexpectedly reduced to about 1/13or less that of the case of no addition.

It is also seen that when titanium is added in a concentration of 0.005at. % or more into zirconium oxide film, diffusion coefficient isreduced as compared with the case of no addition of titanium, and whenit is added in a concentration of 0.02 at. % or more, diffusioncoefficient is unexpectedly reduced to about 1/12 or less that of thecase of no addition.

It is noted from FIG. 11 that, as in the case of FIG. 7, a significantdiffusion coefficient reducing effect is obtainable until hafniumconcentration reaches 15 at. %, but the effect is weakened when hafniumconcentration becomes 12 at. % or higher.

It is also noted that a diffusion coefficient reducing effect can beobtained until titanium concentration goes up to 15 at. %, but theeffect is weakened when titanium concentration becomes 8 at. % orhigher.

It is thus possible to suppress diffusion of oxygen by adding hafnium ina concentration of from 0.01 at. % inclusive to 15 at. % inclusive ortitanium in a concentration of from 0.005 at. % inclusive to 15 at. %inclusive into a film mostly composed of zirconium oxide.

Diffusion of oxygen can also be reduced by adding hafnium in aconcentration of from 0.04 at. % inclusive to 12 at. % inclusive ortitanium in a concentration of 0.02 at. % inclusive to 8 at. % inclusiveinto a film mostly composed of zirconium oxide.

The above advantages can be obtained with little variation even if thecalculation conditions such as film thickness and temperature arechanged.

FIGS. 12 and 13 show an example of the results for a similar analyticalmodel using hafnium oxide as gate dielectric film and cobalt silicidefilm and silicon film as electrodes. D₀ indicates diffusion coefficientof oxygen in case no additional element is contained. FIG. 12 showsadditional element concentration dependency of D/D₀ in the lowconcentration region, and FIG. 13 shows such dependency in the highconcentration region.

It can be seen from FIG. 12 that, as in the case of FIG. 8, whentitanium is added in a concentration of 0.01 at. % or more in hafniumoxide film, diffusion coefficient is reduced as compared with the casewhere no titanium is added, and when it is added in a concentration of0.03 at. % or more, diffusion coefficient is unexpectedly reduced to1/13 or less that of the case of no addition.

It can be also known from FIG. 13 that, as in the case of FIG. 9, thediffusion coefficient reducing effect is observed until titaniumconcentration reaches 15 at. %, but the effect is weakened when titaniumconcentration is 10 at. % or more.

It is thus possible to reduce diffusion of oxygen by adding titanium ina concentration of from 0.03 at. % inclusive to 10 at. % inclusive intoa film mostly composed of hafnium oxide.

Oxygen diffusion can be reduced more intensely and steadily by addingtitanium in a concentration of from 0.03 at. % inclusive to 10 at. %inclusive into a film mostly composed of hafnium oxide.

These advantages are provided with little variation even when thecalculation conditions such as film thickness and temperature arechanged.

In the foregoing calculation examples, cobalt silicide film and siliconfilm are used as electrodes, but similar effect can be obtained by usingother materials. Preference of use of cobalt silicide and silicon,however, is demonstrated by the following calculation example. FIGS. 14and 15 show the results of calculation of diffusion coefficient ofoxygen for various electrode materials when using as analytical model astructure in which a 3 nm thick electrode film is formed on a 3 nm thickgate dielectric film. Shown here is diffusion coefficient of oxygen at300° C. in case no additional element is contained, with FIG. 14 showingthe results when gate dielectric film is composed of zirconium oxide,and FIG. 15 showing the results when gate dielectric film is composed ofhafnium oxide. It can be learned from FIGS. 14 and 15 that when cobaltsilicide and silicon are used as electrode materials, diffusioncoefficient is unexpectedly smaller than the case where other electrodematerials are used. It is therefore more preferable to use cobaltsilicide and silicon as electrode materials for reducing diffusion ofoxygen.

FIG. 16 shows a sectional structure of the principal part of thesemiconductor device according to the second embodiment of the presentinvention. A major difference of this second embodiment from the firstembodiment is that the gate dielectric film is of a two-layer structurecomprising first gate dielectric films 6 a, 7 a and second gatedielectric films 6 b, 7 b. Second gate dielectric films 6 b, 7 b aremostly composed of zirconium oxide or hafnium oxide for meeting therequirements for miniaturization and high functionality. For first gatedielectric films 6 a, 7 a, there is used, for instance, silicon oxide,zirconium silicate or hafnium silicate as main constituent. It isthereby possible to produce the same advantage as in the firstembodiment and to improve thermal stability of second gate dielectricfilms 6 b, 7 b. In the above example, gate dielectric film is of adouble-layer structure, but it is also possible to provide a structureof three or more layers for gate dielectric film although not shown inthe drawings.

FIG. 17 shows a sectional structure of the principal part of thesemiconductor device according to the third embodiment of the presentinvention. A major difference of this third embodiment from the secondembodiment is that gate electrode film is of a two-layer structurecomprising first gate electrode films 8 a, 9 a and second gateelectrodes films 8 b, 9 b. Other mechanisms can be the same as those inthe second embodiment. It is more preferable to use cobalt silicide orsilicon as main constituent of first gate electrode films 8 a, 9 a asthese materials are more repressive against diffusion of oxygen. Forsecond gate electrode films 8 b, 9 b, it is more preferable to use afilm mostly composed of a metal such as tungsten or molybdenum so as toreduce electric resistance of the whole gate electrodes. In this case,although not shown in the drawings, another conductive film may bedisposed between first gate electrodes films 8 a, 9 b and second gateelectrode films 8 b, 9 b. As such another conductive film, it is morepreferable to use a film, such as TiN film or WN film, having the effectof preventing mutual diffusion of first gate electrode films 8 a, 9 aand second gate electrode films 8 b, 9 b.

As described above, according to the third embodiment of the presentinvention, it is possible to obtain the same advantages as in the secondembodiment and an additional advantage of reducing electric resistanceof gate electrodes.

FIG. 18 shows a sectional structure of the semiconductor deviceaccording to the fourth embodiment of the present invention. A majordifference of this fourth embodiment from the first, second and thirdembodiments is that this embodiment has a capacitor element 103 forstoring information having a structure comprising a laminate ofconductive barrier film 114, capacitor lower electrode 115, highlydielectric or ferroelectric oxide film 116 and capacitor upper electrode117. It is known that highly dielectric or ferroelectric oxide film 116does not exhibit its advantageous properties unless it is subjected toheat treatment. So, it is necessary to carry out heat treatment of about600° C. or higher, more preferably about 700° C. or higher in theproduction process. During this heat treatment, cobalt or nickel isliable to diffuse from contact wiring film 119 into silicon substrate101, and oxygen is liable to diffuse from gate dielectric film 106 intosilicon substrate 101, so that in the case of a semiconductor memoryhaving highly dielectric or ferroelectric oxide film, there is a greaternecessity of controlling diffusion of said elements.

The principal structure of the semiconductor device according to thefourth embodiment is explained below. The semiconductor device of theinstant embodiment comprises metal oxide semiconductor (MOS) transistors102 formed in the active region on the major surface of siliconsubstrate 101, and capacitor elements 103 for storing informationdisposed on said transistors. 104 indicates element separation, and 109shows insulating film. Insulating film 112 is a film for inter-elementalseparation. MOS transistor 102 of memory cell is composed of gateelectrode film 105, gate dielectric film 106 and diffusion layer 107.For gate dielectric film 106, zirconium oxide or hafnium oxide is usedas main constituent for meeting the requirements for miniaturization andhigh functionality. This gate dielectric film 106 can be formed, forexample, by CVD or sputtering. In case of using zirconium oxide as mainconstituent of gate dielectric film so as to suppress diffusion ofoxygen into silicon substrate or gate electrodes, it is more preferableto incorporate hafnium or titanium as additional element into gatedielectric film. In case of using hafnium oxide as main constituent ofgate dielectric film, it is preferable to incorporate titanium asadditional element into gate dielectric film. Gate dielectric film mayhave a structure of two or more layers as in the second and thirdembodiments. It is more preferable to use cobalt silicide or silicon asmain constituent of gate electrode film 105 as these materials aresuppressive of diffusion of oxygen. Gate electrodes may have a structureof two or more layers as in the third embodiment. This electrode film105 can be formed, for example, by CVD or sputtering. Also, insulatingfilm 9 composed of, for instance, silicon oxide is formed on the top andaround the side wall of said gate electrode film 105.

Bit line 111 is connected via plug 110 to diffusion layer 107 at a sideof MOS transistor for memory cell selection. The top of MOS transistoris entirely covered with insulating film 112, which is composed ofboron-doped phospho silicate glass (BPSG) film, spin on glass (SOG) filmor silicon oxide or nitride film formed by CVD or sputtering. Capacitorelement 103 for storing information is formed on insulating film 112covering MOS transistor. This capacitor element 103 for storinginformation is connected to diffusion layer 108 at the other side ofsaid MOS transistor for memory cell selection via plug 113 composed of,for example, polycrystalline silicon and wiring film 119 for contactmostly composed of cobalt silicide or nickel silicide. Said capacitorelement 103 for storing information has a structure comprising,laminated from bottom upwards, conductive barrier film 114, capacitorlower electrode 115, high dielectric constant oxide film 116, andcapacitor upper electrode 117. This capacitor upper electrode 117 iscovered with insulating film 118. Tantalum oxide, for instance, is usedas main constituent of oxide film 116. Zirconium oxide or hafnium oxideis also usable. Capacitor element 103 for storing information is coveredwith insulating film 115.

It is preferable to use silicon film having (111) orientation forcapacitor upper electrode or capacitor lower electrode so as to preventdiffusion of oxygen into these electrodes during heat treatment.

In case of using zirconium oxide as main constituent of oxide film 116,it is more preferable to incorporate hafnium or titanium as additionalelement into said film 116.

When using hafnium oxide as main constituent of oxide film 116, it ismore preferable to incorporate titanium as additional element into oxidefilm 116. Capacitor element 103 is covered with insulating film 118.

In the fourth embodiment of the present invention, as described above,there can be obtained the similar advantage as in the first embodiment.

As another embodiment of the present invention, it can be a system LSIcomprising memory LSI such as used in the fourth embodiment and logicLSI such as used in the first, second and third embodiments, both beingprovided on the same one substrate.

It is also possible to obtain information-storing capacitor element 103with high performance by first forming vertical grooves, then formingcapacitor lower electrode 115, further forming high dielectric constantfilm (oxide film 116 having high dielectric constant), then formingcapacitor upper electrode 117, and after forming said high dielectricconstant film or capacitor upper electrode 117, conducting ahigh-temperature (850-950° C.) heat treatment.

FIG. 19 shows a thin film transistor (TFT) structure in thesemiconductor device according to the fifth embodiment of the presentinvention. This semiconductor device of the fifth embodiment of thepresent invention has a TFT structure in which, as shown in FIG. 19,there are formed on, for instance, a glass substrate 201, a conductivefilm (silicon film) 202 composed of polycrystalline silicon, aninsulating film (gate dielectric film) 203 mostly composed of zirconiumoxide or hafnium oxide, a conductive film (gate electrode film) 204composed of polycrystalline silicon, for instance, an n-type siliconfilm 205, a drain electrode film 206, a source electrode film 207, andan insulating film 208.

In order to prevent oxygen from diffusing out from insulating film 203mostly composed of zirconium oxide or hafnium oxide, a silicon filmhaving (111) orientation is used as conductive film 202 or 204.

By these means, it is possible in the fifth embodiment of the presentinvention, too, to prevent diffusion of oxygen from insulating film 203and to realize a semiconductor device having a TFT structure withimproved characteristics.

The following advantages are derived from the embodiments of the presentinvention.

A silicon substrate of which the surface is (111) crystal face is used.

Hafnium or titanium is added to zirconium oxide, or titanium is added tohafnium oxide in the insulating films.

Cobalt silicide or silicon is used as electrode material which isdeterrent against diffusion of oxygen through the interface withinsulating film mostly composed of zirconium oxide or hafnium oxide.

Further, a polycrystalline silicon film having (111) orientation is usedfor the semiconductor devices having a TFT structure.

By these means, it is possible to prevent deterioration ofcharacteristics concomitant to miniaturization and to realize asemiconductor device with high reliability.

It is further possible to realize a miniaturized and high-yieldsemiconductor device.

It is also made possible to realize a semiconductor device having a gatestructure which controls diffusion of oxygen at the interface betweensilicon substrate and gate dielectric film.

There is further realized a semiconductor device having a TFT structure,which suppresses diffusion of oxygen at the interface between siliconfilm and gate dielectric film.

It should be further understood by those skilled in the art that theforegoing description has been made on embodiments of the invention andthat various changes and modifications may be made in the inventionwithout departing from the spirit of the invention and the scope of theappended claims.

1. A semiconductor device comprising a silicon substrate, gatedielectric films mostly composed of hafnium oxide and formed on a majorsurface of said silicon substrate, and gate electrode films formed incontact with said gate dielectric films, said major surface of saidsilicon substrate being parallel to Si (111) crystal face.
 2. Asemiconductor device according to claim 1, wherein said gate electrodefilms are mostly composed of cobalt silicide or silicon.
 3. Asemiconductor device according to claim 2, wherein said gate dielectricfilms contain titanium in a concentration of from 0.01 at. % inclusiveto 15 at. % inclusive.
 4. A semiconductor device according to claim 2,wherein said gate dielectric films contain titanium in a concentrationof from 0.03 at. % inclusive to 10 at. % inclusive.
 5. A semiconductordevice comprising a silicon substrate, gate dielectric films formed on amajor surface of said silicon substrate, gate electrode films formed onsaid gate dielectric films, and wiring films mostly composed of cobaltsilicide or nickel silicide, said major surface being formed so as to be(111) crystal face of the substrate, wherein the substrate having (111)orientation is used to prevent diffusion of cobalt from the wiring filmsinto the substrate, wherein said gate dielectric films are mostlycomposed of zirconium oxide.
 6. A semiconductor device according toclaim 5, wherein said gate electrode films are mostly composed of cobaltsilicide or silicon.
 7. A semiconductor device according to claim 5,wherein said gate dielectric films contain hafnium in a concentration offrom 0.01 at. % inclusive to 15 at. % inclusive.
 8. A semiconductordevice according to claim 5, wherein said gate dielectric films containtitanium in a concentration of from 0.005 at. % inclusive to 15 at. %inclusive.
 9. A semiconductor device, comprising: a substrate having(111) crystal orientation; a gate oxide provided over the substrate, thegate oxide including zirconium oxide or hafnium oxide; a gate electrodeoverlying the gate oxide; first and second conductive regions providedon the substrate and on opposing sides of the gate electrode, whereinthe gate oxide is contacting the substrate and includes titanium orhafnium, the gate electrode including cobalt silicide or cobalt siliconto prevent oxygen diffusion into the gate electrode from the gate oxide,wherein the (111) crystal orientation of the substrate reduces diffusionof materials into the substrate from the gate oxide and gate electrode.10. The device of claim 9, wherein the gate oxide is about 3 nm thick.11. The device of claim 9, further comprising: a via plug coupled to thefirst conductive region, the via plug including a metal plug and aconductive film, the conductive film provided between the metal plug andthe first conductive region.
 12. The device of claim 9, wherein the gateoxide includes a first layer and a second layer, the first layercontacting the substrate and including silicon oxide, zirconiumsilicate, or hafnium silicate, the second layer overlying the firstlayer and including zirconium oxide or hafnium oxide.
 13. The device ofclaim 9, where the gate electrode includes a first electrode and asecond electrode, the first electrode overlying the gate oxide andincluding cobalt silicide or cobalt silicon, the second electrodeoverlying the first electrode being primarily metal.
 14. The device ofclaim 13, wherein the gate oxide is about 3 nm and the second electrodeis tungsten or molybdenum.